Siemens Power Technologies International
Short-circuit calculations
PSS®E
At a glance
PSS®E Short Circuit module has a number of short circuit
calculation algorithms to meet the diverse needs of fault
analyses. All algorithms are self-contained analyses in
PSS®E. They require a valid power flow working case and
the power system sequence data. The following types of
unbalances or faults can be applied at any bus / transmission line on any phase.
■ three-phase (3PH) faults
■ single-line-to-ground (LG) faults with specified fault
impedances
■ double line-to-ground (LLG) faults with specified fault
impedances
■ line-to-line (LL) faults with specified fault impedances
■ one phase opened or two phases closed
■ two phases opened or one phase closed
■ one end opened
One or more of these faults can be applied simultaneously.
It can simulate one or all fault types at one bus or all system or sub-system buses in one run, thereby reducing the
analysis time.
The challenge
The electrical utilities and industries need to design, operate, protect and maintain the electrical installations as per
fault current duties. To determine the worst fault duties,
one needs to consider various types of faults and number
of network scenarios; potentially leading to a large number
of short circuit calculations. Assembling and validating the
vast electrical network data required for fault analyses is
cumbersome and time consuming.
Our solution
Fault analysis in PSS®E is based on a symmetrical component system representation. The positive-sequence system
model as established in power flow is used directly in fault
analysis. The negative- and zero-sequence system data are
appended to and saved with the power flow case data,
needing only one data file to carry out both power flow
and short-circuit analysis. No additional validation of such
data is required. The various network elements, such as
generators, motors, transmission lines, transformers, loads,
shunts, DC devices, are modeled in the highest level of
detail. There are provisions and access toward applying
simplified models for these components, thereby giving the
highest degree of freedom in modeling different network
elements. PSS®E handles special network simulations such
as:
■ Symmetrical and asymmetrical breaking three-phase
short-circuit currents for a given circuit breaker contact
parting time that includes machine internal flux decay
effects
■ Isolated ungrounded subsystems where one or more of
the sequence networks is separated into unconnected
subsystems
■ Singular fault constraints which arise by the application
of simultaneous faults, especially in combinations involving open phases
■ Two and one-phase systems
The fault sequence and phase currents (Ia1, Ia2, Ia0, IA, IB,
IC) and voltages (Va1, Va2, Va0, VA, VB, VC) are available in
text reports and can also be displayed on one line diagrams
of the network model or exported to Python lists. Reports
presenting “Total Fault Currents” and “Fault Currents
Contributions” at N levels away from faulted bus are also
available.
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FLAT
ANSI
■ Sets up classical short-circuit assumptions to a power
flow working case.
■ Calculates the following fault quantities according to the
ANSI C37.5 -1979 standard:
SCEQ
■ Symmetrical fault MVA at breaker fault duty time
■ Calculates positive-, negative- and zero-sequence short
circuit system equivalents.
■ Symmetrical fault current at breaker fault duty time
SCMU
■ Calculates instantaneous fault currents for one or more
simultaneous shunt or series imbalance with and without initial system loading conditions included.
ASCC
■ Calculates instantaneous fault currents for a series of
faults at one bus or all system or sub-system buses with
and without initial system loading conditions included.
■ Asymmetrical fault current at breaker fault duty time
■ ANSI X/R ratio
■ ANSI multiplying factor
IECS
■ Calculates the following fault currents per IEC 60909 2001 standard:
■ I”k Initial RMS symmetrical short-circuit current
BKDY
■ ip(B) Peak short-circuit current by IEC 60909 Method
B
■ Calculates the following circuit breaker interrupting duty
currents for a given pre-disturbance condition:
■ ip(C) Peak short-circuit current by IEC 60909 Method
C
■ RMS Symmetrical initial fault current
■ Peak DC component of fault current at breaker fault
duty time and
■ RMS symmetrical breaking fault current at breaker
fault duty time
■ RMS asymmetrical fault current at breaker fault duty
time
■ Peak asymmetrical fault current at breaker fault duty
time
■ ib (DC) DC component of asymmetrical breaking current
■ ib (SYM) RMS Symmetrical short-circuit breaking current
■ ib (ASYM) RMS Asymmetrical short-circuit breaking
current
The fault calculations can be launched from PSS®E GUI or
PSS®E batch scripts (BAT_, Python, IDEV, or IPLAN)
Siemens AG
Power Technologies International
Freyeslebenstrasse 1
91058 Erlangen
Germany
Siemens Industry, Inc.
Power Technologies International
400 State Street
P.O. Box 1058
Schenectady, NY 12301-1058 USA
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